Circuit interrupter



Jan. 12', 1932. A, C, CRAGO 1,841,091

CIRCUIT INTERRUPTER Filed Aug. 29, 1927 Fly. 5. F1914. .my 5. F13/.61 ffy 7.

IHIIIIII IIIIHH NNUU IIIIHII! Hl ml; @l @l INVENTOR @y Alan acragou;

Samuel D.Crago, Administrator g Patented Jan. 12, ,1932

` UNITED STATES PATENT OFFICE 'ALAN C. CRAGO, DECEASED, LATE OF PITTSBURGH, PENNSYLVANIA, BY SAMUEL D.

CRAGO, ADMINISTRATOR, OF PITTSBURGH, PENNSYLVANIA, ASSIONOR T WEST- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, .A4 CORPORATION OF PENN- SYLVANIA GIRCU IT INTERRUPTER The present invention relates to circuit in.- terrupters and particularly to circult interrupters which accomplish their purpose by forcing the arc incident to the separation of' their contacts into a deionizing chamber'- which comprises means, such as a plurality of superposed metallic plates, enabling them to interrupt currents of large power.

`While the invention is here shown as embodiedin a circuit interrupter for alternating-current service, and while particularly eiective in such service, many of the principles of the invention are equally'applicable to circuit interrupters for direct-current circuits. I

One object of the invention is to provide means to assist in extinguishing the arc incident to the opening of thecontacts of a cirlcuit breaker,'by connecting, in series therewith, a saturated-cornl inductance.

Another object of the invention is to provide a device wherein a single deionizing chamber is utilized to Vfirst extinguish the arc incident to separating a pair of contacts shunted by a saturated-core inductance, and is then employed to extinguish an arc incident to separating a pair of'contacts in series with said inductance.

A further object of the invent-ion is to provide means wherein a single deionizing chamber is employed to interrupt an arc incident to the opening of a pair of contacts shuntedl by a saturated-core inductance amnd is nthen utilized to extinguish the arc incident to the separation of a pair of cont-acts shunted by a resistor.

A further object of the invention is to provide a. device in which an arc-interrupting device of the kind described in copending application, Serial No. 216,033 .of Alan C.

Crago, deceased, for a circuit interrupter,

assigned to the Westinghouse Electric &

Manufacturing Company, is operated in series with a saturated-core inductance.

Other objects of the invention will become apparent through reading the following speciication 'in connection with the drawings, in which;

Figure 1 is a side view of a circuit interrupter embodying the invention,

Fig. 2 is a detail view of a deionizing metallic plate utilized in the deionizing chamber of one form which may be used in connection with the invention.

Figs. 3 to 7, inclusive, are illustrative diagrams showing circuit connections of the elements constituting the invention at various stages in the course of operation thereof to open a circuit.

Copending applications Serial No. 54,930, filed September 8, 1925, and Serial No. 181,289 filed April 6, 1927, of Joseph Slepian assigned to the Westinghouse Electric & Manufacturing Company, show arrangements in which the arc incident to the opening of circuit breakers in air is forced into a deionizing chamber and therein extinguished at the zero point of an alternating-current wave. By the employment of such deionizing chambers, it is possible to interrupt currents of large value in circuits of high-voltage which hitherto have only been broken by the use oi oil or other arc-quenching mediums.

In connectionwith the extinguishing of arcs and such deionizing structures, it has been found that the amount of current which can be interrupted may be increased if resistances of suitable values' are connected in shunt to the contacts when they first separate and are later connected in series therewith. The arc is, so to speak, interrupted in two or more stages instead of at a single stroke.

It has been found that an inductance in series with an arc incident to separation of the contacts of a circuit interrupter of the foregoing type assists in the extinction of the arc,`it beingl possible, when such a re@ actor is used, to interrupt a given current with a much larger resistance inv shunt across the arcing contacts. As a consequence of this condition, the interruption of the are may take place in fewer sta es, and with correspondingly fewer steps o auxiliary resisteffective value for higher instantaneous currents, there is a decided advantage in providin'g the inductance with a core of such dimensions that. it is highly saturated for the larger values of currentwhich the eircuit interrupter is called upon to handle.

This is due to the fact that the are is extinguished near the zero point of ,the wave where the current is relatively small so that the core is not saturated and its inductance is relatively large so that it retards the rate of voltage rise, thus giving increased 'timeto a pair of separable contacts which open when the circuit is tobe interrupted and cause the line current to transfer to a path through the' inductance. The act oi' separating the contacts produces an arc between them and it is highly desirable to provide means by which this arc may be extinguished quickly and eie'ctively. It would be possible to provide a separate deionizing chamber, oit the type described in the above-mentioned applications of Joseph Slepian, to do this; but, since such deiohizing chambers are relatively expensive, it is preferable to utilize a single chamber only for extinguishing all the arcs incident to the complete o ening of the circuit, and to provide means y which it is first used to extinguish the arc incident to causing current to flow through the saturated-core inductance and then to utilize it for extinguishing the remaining arcs incient to complete interruption of current A specific arrangement, by means of which it is proposed to accomplish this general result, shows a circuit breaker comprising main contacts 1 and 2 and a bridging member 3 of conventional type. When the circuit breaker is actuated to its open position, the arm fl supporting the bridging member 3 movestabout its hinge 5 to the right, separating the bridging member 3 from the main contacts. It is usually desirable to provide, in addition to the bridging member 3, an arcing contact 6 which breaks its Contact later than the main contacter. Such auxiliary contacts are well known in the art.

The upper end ot the arm l supports an arcuate member Z faced with a stuitable insulator 8 upon which are placed a series of metallic blocks 9, 10, 11 and 12. Between the contact blocks 9 and 10 is connected a saturated-core inductance 13. This consists simply 'of a winding on an 'iron core so dimensioned as to be saturated magnetically even at relativel small currents. Between the contact bloc s 10, 11 and 12 are connected, by any suitable means, such as iiexible leads, a plurality of resistance sections.

The upper faces of the blocks 9, 10, 11 and 12 are machined to be concentric with the hinge 5. Above the single arm 4 is positioned the deionizing chamber 15 which comprises a pair of metallic end-plates 16 and 17 faced on each side by insulating plates to form an inclosure which is open at the top. This chamber has, at its bottom end, a pair of arcing horns 18 and 19 against the lower faces of which the Contact blocks 9, 10, 11 and 12, aforesaid, make a sliding engagement. The lower part of the deionizing chamber 15 is empty but, in its'upper portion, are located a series of spaced vertical metallic plates of the Jform shown in detail in Fig. 2. -The plates may be of copper, 115 of an inch thick and spaced apart y of an,inch by a series of washers of fish paper-or other suitable insulation. The lower edges ofthe metallic vplates are provided with notches of substantially V-shape, as shown in Fig. 2, and these notches aline when the plates are assembled in the deionizing chamber to form a V-shaped groove which greatly7 increases the effectiveness of the chamber in extinguishing the arc.

The lower portions of the insulating side plates of the deionizing-chamber above-mentioned, are held tightly between the poles of a blowout magnet 21, comprising an iron yoke 22 and an exciting winding 23 therefor. One end of the blowout-magnet winding is connected to the contact terminal 1 and the other end is connected to one of the end plates 16. The other end plate L'Zfis connected, through arm 4 and conductor '25 to the other main contact 2. An inspection of the drawings will show that the blowout magnet and the deionizing chamber 15 are thereby connected in series across the main contacts 1 and 2.

The deionizing chamber above described is not part of the present invention, but forms the subject-matter of the Slepian application Serial No. 181,289 tiled April 6, 1927 abovementioned.I Such being the general structure of the circuit breaker, its mode of operation in opening the circuit will now be described. When the main bridging member 3 and the auxiliary Contact 6 open the circuit 'be-- tween the main contacts 1 and 2, contact member 9 is so positioned as to bridge the arcing horns 19 and 18. The opening of the bridge across members 1 and 2, however, forces current to flow through the winding 23 of the blowout magnet to the endplate 16, and then through the arcing horn 18, contact member 19, arm 4, and conductor 25 to the other contact 2. Fig. 3 diagrammatically illustrates this stage@ of operation.

A. slight further movement of the arm t breaks contact between the block 9 andthe y arcingyhorn 18, and draws an arc therebetween. This arc is shunted by the saturatedcore inductance 13,r since the Contact 10 is so positioned that it makes contact with the arcing horn 18. Current is, therefore, caused to divide, part of it flowing through the saturated-,core inductance 13 and part of it through an arc in the deionizing chamber 15.

The blowout magnet 21 drives this arc upward into the deionizing structure compris'- ing the superposed plates 20, and forces it into the V-shaped groove therein. As the-current in this arc falls to zero in the course of the alternating-current cycle, the arc path is rapidly deionized because of the contiguity of the metallic plates which tend to dischargeany ions which may impinge upon them. When, in the course of the succeeding alterhating-current wave, the voltage between the end. plates 16 rises, what few ions remain free The foregoing steps, however, leave a certain amount of current flowing through the saturated-core inductance.

A further movement of the arm 4 to the right breaks contact between the contact block 10v and the arc horn 18, and establishes an arc therebetween shunted by the resistor section 28. This process,'it will be seen, is similar to that `which occurred on breaking the contact between contact block 9 and arc horn 18, except that the saturatedcore inductance is now in series with themain current. As a consequence of this latter fact,

the value to which the current can rise and the voltagev which will -existacross the contacts 10 and 18 after the alternating current passes through zero, are strictly limited. Since no current flows between arc. horn 19 and contact 9, they part company without the development of any arc between them.

' A further movement of the arm 4 transfers the arc to the other arei'ng horn 19, and the blowout umagnet 22 forces it up into the deionizing structure where it is extinguished in its turn. Fig. 5 represents the circuit con nections at this stage of the operation.

A further movement of the arm 4 then breaks contact between the block '11 and the arc horn 18, shunting the arc therebetween by the resistor section 29, and placing resistor section 28 in series with the main line to further limit the rise of current, as shown u diagrammatically in 6. The arc between members 18 and 11 is extinguished precisely in the manner which has been described' beforeI and finally a. contact block 12 draws lan arc from the arc horn 18 which is shunted by no resistance, but which is so limited by the resistor sections 28 and 29 and inductance 13, which are now connected in series with the main line, as indicated in Fig. 7, that the deionizing structure is capable of completely interrupting current flow in the circuit.

It has also been found that the effectiveness of the saturated-core inductance may-be increased in certain instances if it is shunted by a resistance or a condenser. The use of a condenser permits the magnetic iux in the iron core to vary over a considerably wider range than is possible where a mere resistor is used, and thereby makes possible a design in which the size of the core and that of the winding are considerably decreased.

Accordingly, there has been provided` means by which a single deionizing chamber may be made to interrupt the arcs formed when a' plurality of resistance sections are connected in series with a circuit in which it is desired to interrupt current fiow, thereby making possible the interruption of'larger amounts of power than would be-possible were the circ-uit interrupted at a single operation.

While this invention has been described.

as used in connection with a specific arc-extinguishing means,.it will be obvious that it is not limited to such use but is of general application to effect circuit interruption even when no special means are provided to extinguish the arcs incident to separation of the contacts.

The principles which have been embodied in the circuit breaker herein described are` with said inductance,means for' extinguishf ing said are and means for establishing an are in series with said inductance at the point of said extinguishment.

2. In combination with an iron-core inductance, ine-ans to establish an arc in shunt with Isaid inductance, said inductance being proportioned to be magnetically saturated by a fraction of the current ,in said arc, means for establishing an arc in series with said inductance and means for extinguishing the last said arc.

3. In combination with an iron-core inductance, means to establish an are in shunt with said inductanee, said-inductance bein roportioned to be magnetically saturate y a fraction of the current in said arc, means for extinguishing said arc and separable contacts in series with said inductance.

4. In combination with an iron-core inductance, means to establish an arc in shunt with said inductance, ,means lfor establishing an arc in series with said inductance and means for deionizing both of said arcs.

5. In combination with an iron-core inductance, means to establish an are in shunt with said inductance, said inductance bein proportioned to be magnetically saturate by a fraction of the current in said arc, means for deionizing said arc and means for establishing an arc in series with said inductance.

6. In combination with an iron-core inductance, means to establish an are in shunt with said inductance, said inductance being proportioned to be magnetically saturated by a fraction ofthe current in said are, means for deionizing said are, means to force said arc towards said deionizing means, means for establishing an are in 'series with said inductance, and means to force said second are toward said deionizing means.

7. In combination with an iron-core inductance, means to establish an are lin shunt with said inductance, said inductance being proportioned to be magnetically saturated by a fractionof the current in said arc, means for deionizing an arc, means to force said arc towards said deionizing means, a pair oi separable contacts in series with said inductance, and means to force thearcincident to the opening of 'said-'contacts towards said deionizing means. 8. In combination with an iron-core inductance, means to establish an arc in shunt with said inductance, means for deionizing an are, means to force said `are towards said deionizing means, a pair of separable contacts in series with said inductance', and means to force the are incident to the opening of said contacts towards said deionizing means. l

9. In combination with an iron-coreI inductance, means to establish an are in shunt with said induetance, means for extinguishing said arc, a blowout magnet for said are and means for establishing an arc in series with said inductance and both ot said arcs being extinguished by the same extinguishing means.

10. In combination with an iron-core induetance, means to establish an arc in shunt with said inductance, said inductance being' proportioned to be magnetically saturated by a fraction of the current of said are, a blowout magnet for said are positioned 'to 'force it into said extinguishing means, and means for establishing an are in series with said inductance.

11. In a circuit interrupter, a pair of separable contacts for drawing an are, an ironcore induetance connected in shuntI with said contacts, means for extinguishing the arc drawn between said contacts, and separable contacts in series with said inductanee and adjacent to said extinguishing means when establishing a second arc.

l2. In a circuit interrupter, a pair of separable contacts for drawing an arc,- an ironcore inductance connected in shunt with said contacts and proportioned to be magnetically saturated by a 'fraction of the rated current of said circuit interrupter, means for extinguishing an arc drawn between said contacts, and separable contacts in series with said inductance.

13. In a circuit interrupter, a pair of separable contacts for drawing an are, an ironcore induetance connected 1n shunt with said arable contacts for drawing an arc, an ironcore inductance connected in shunt with said contacts and proportioned to be magnetically saturated by the full load current of said circuit interrupter, means for extinguishing an arc drawn between said contacts, a blow out magnet positioned to force said are towards said extinguishing means, and separable contacts in series with said induetance forestablishing an arc in the vicinity of the blowout magnet and extinguishing means.

15. The method of extinguishing an arc which comprises shunting said arc by an iron-core inductance proportioned to he saturated by a fraction of the current in said arc, deionizing said are, drawing a second arc in series with said induotance ionizing said second arc.

16a The method et interrupting a circuit which comprises opening a pair of separable contacts in said circuit which are shunted by an inductance proportioned to be saturated by a fraction of the current of said circuit, forcing any are drawn between said contacts 'towards a structure adapted to deionize it,

and deopening separable contacts in' series with: said inductance, and forcing any arc result- -ing thereat into contact with said deionizing structure.

In testimony whereof, I have hereunto subscribed my name this 18th day of August, 1927..

SAMUEL D. CRAGO, Administrator of the Estate of Alam U. Urago,

Deceased. 

